1) What are the ZEROs?
The ZEROs are the simplest type of transformer called an auto-transformer or autoformer. They are used to multiply the impedance of any speaker so that it "feels" like the optimum load for the amplifier being used. They are very helpful in matching speakers to amplifiers. By adjusting the speaker's impedance, both the damping factor and the maximum power transfer of the amp/speaker can be tailored for the best sound.
I have been told that the ZEROs can be used as a sliding scale to adjust the sound of a system anywhere from the sound of the tube amplifier in use, to the sound of a very good solid state amplifier, or choosing something in between.
I consider the ZEROs as a tool to get the most out of low impedance speakers, and as a means to freely adjust the amp/speaker damping factor.
2) What is Damping Factor?
The damping factor is simply the ratio of the speaker's impedance over the amplifier's output impedance. For example if a 4 ohm speaker is being driven by an amplifier that has a output impedance of 2 ohms, then the damping factor is 4/2 = 2.
Now using the ZEROs to make the 4 ohm speaker a 16 ohm speaker, the damping factor becomes 16/2 = 8.
A woofer that is "under damped" will sound uncontrolled and boomy. A woofer that is "over damped" will sound thin and lean. A speaker's woffer will sound best when it is "critically damped", This is where it will extend lowest in frequency without "ringing".
3) What are the Multiplication factors available?
The multiplication taps are: (1.37x), (2x), (2.75x), (4x), (8x), and (16x). So a 4 ohm speaker can be made to look like a16 ohm speaker by using the (4x) taps.
4) How will I know which multiplication factor to chose?
Start by using the 2x and then the 4x multiplication factors to get the feel of the ZERO's effect. As the speaker's impedance is increased you will notice a decrease in distortion, an increase in resolution, and a tightening of bass control. Start with a low multiplication factor and step up to higher multiplication factors. You will know when you have gone to far when the system starts sounding like a dry solid state amplifier. This happens when the amplifier has over damped the speakers. When this happens, the multiplication factor needs to be reduced again. Trust your ears, and when you achieve the best sound possible, you are done.
5) What improvements can I expect to hear by adding the ZEROs to my system?
Both my experience and reports from many many ZEROs users have these common results:
A) Lower distortion "sounds cleaner" (due to an easier load on the amplifier)
6) Who is using the ZEROs?
The ZEROs users are world wide. I have shipped ZEROs to: Canada, England, Turkey, Sweden, Scotland, Australia, Portugal, Holland, Puerto Rico, Malaysia, Italy, and many of the States in the USA.
The most common users are running OTL amplifiers from Atma-Sphere and Transcendent Sound. Simply because these are the circles I am in, so these are the people that know of the ZEROs. Others are using them on SET amps with great results. I have been told by a European speaker manufacture that every amplifier from 2-7w SET, 20w p-p, 50w p-p, to a 200w solid state amp they tried sounds better driving a 16 ohm speaker rather than a 4 or 8 ohm speaker of identical design. They know, they tested it.
7) What is the difference between the ZEROs autoformer and a typical tube amplifier's transformer?
The ZEROs have a few advantages over "typical" tube amp transformers:
A) The music comes out on the same winding wire that it goes in on so the music does not have to pass from a primary winding to a secondary winding.
8) Doesn't adding the ZEROs to my Output-Transformer-Less (OTL) Amplifier defeat the benefits of the OTL design?
The ZEROs were originally designed to maximize the full benefits of the OTL amplifier by changing the speaker's load impedance to the Maximum Power Transfer Region of the amplifier being used.
The ZEROs are not a amplifier fix, they are a speaker fix. It is a great disfunction to music loving audiophiles for speaker manufactures to be making 4 ohm speakers with 3 or 2 ohm impedance dips, and then expect amplifiers and speaker cables to be able to transfer music into a load approaching a dead short. The ZEROs simply multiply the impedance of the speaker in use, and do it so transparently that not one ZEROs users has ever reported any sonic signature the ZEROs add to the music.
9) Should I add the ZEROs close to my speakers or close to my amplifier?
Adding the ZEROs close to the speakers means that not only does the amplifier benefit from the higher impedance, but the speaker wires benefit as well. This benefit was not expected by me, yet is very real. The inductance and resistance in a speaker wire run is 1/4 less of a problem into 16 ohms as it would be into 4 ohms.
Do what you can to cut the ZERO's speaker leads as short as is reasonable. This is the high current side and is audibly most susceptible to wire length runs.
10) Can I get rid of my speaker wires altogether?
This is reportedly the best way to go. Because of requests, the ZEROs now have 48" leads to connect to the amplifier, and 24" leads that connect to the speakers. In many cases this is enough length to eliminate existing speaker wires. If not, the 48" leads can be shortened and have binding posts add to except the speaker wires.
11) How do I add connectors to the ZERO's leads?
Most ZEROs users simply do-it-themselves. This way they are able to shorten the leads to the length needed (excess wire is not good for music), and add the connectors of their choice. Some ZEROs users have fitted them into pre-made boxes with binding posts for all of the connections. For the non do-it-yourself people, I have added the needed connectors at cost (about $20).
12) What will the ZEROs do for my already transformer coupled tube amp?
What has been really fun is to hear for myself, and hear reports from others, is that transformer coupled tube amps sound better driving higher impedance speakers (made so with the ZEROs autoformers). Since I trust my own ears, I have to ask myself why did adding the ZEROs autoformer to the speaker and moving the transformer coupled tube amp off of the 4 ohm tap, on to the 8 ohm (or16 ohm if available) tap improve the sound? It really doesn't make sense at first, adding another component to improve the sound when a 4 ohm tap is already available for the 4 ohm speaker. Again I can't prove anything, but I speculate that it is possible that the transformer coupled amp sounds best when the entire secondary winding is
used, provided that it is driving the impedance it wants to see (and the ZEROs do this). Maybe it is because the feedback loop (if used) is usually not taken off of the 4 ohm tap. Maybe it is because there is a smaller impedance ratio from a few thousand ohms down to 16 ohms, rather than down to 4 ohms. Maybe it is only the speaker wire that becomes a better transfer of music driving 16 ohms instead of 4 ohms.
13) Why don't speaker manufactures just make speakers with 16 ohm impedance if it will make systems sound better.
A 4 ohm speaker will draw four times more current from a solid state amplifier than from a 16 ohm speaker at the same volume setting, thus sucking four times more power from the amplifier (again at a set volume setting). This helps make the speaker play louder in the showroom when it is going up against competitors. I think "perceived" efficiency helps sell speakers, and you got to sell them to stay in business.
This has gotten so out of hand that the speaker industry stopped rating a speakers "efficiency" and started rating it as speaker "sensitivity", which is how loud a speaker will play at a given voltage rating no matter how much current (and power) it is sucking out of the amplifier.
This aspect of the speaker industry has got to change back. After meeting with and then writing a letter to the Editor of Stereophile on this issue, John Atikson has noted in his "Measurements" sections of low impedance speakers, that the speaker is actually drawing
more power than the 1 watt standard. It's a start, so good for him. Below are three examples:
1) July 01, p.65, Martin Logan Prodigy review:
"....indicates it to be, as specified, basically a 4 ohm load through much of the audio band. This will mean the speaker will actually draw 2W from the amplifier from that voltage level, not 1W."
2) August 01, p.70, Krell LAT-1 review:
"However, as shown by its impedance plot, it is a 4 ohm design, drawing 2W rather than 1W from the partnering amplifier to reach this measured sensitivity."
3) August 01, p.79, Audio Physic Avanti III review:
"...revealed it to a 4 ohm design; ie, it actually draws two watts from the amplifier to raise the rated sound pressure level."
14) Who is Paul Speltz and where can I ask more question?
I am not in business. I'm just a music loving Electronic Engineer, having fun with my
hobby and I came across a simple tweak that many people are enjoying. Feel free to email me with any questions at:
Enjoy, Paul
B) Firmer bass (due to an increased damping factor)
C) Higher resolution (due to an easier load on the amplifier)
D) More extended and better focused high frequency
B) There is no DC current to contend with. When a transformer is made to accommodate a DC field, its audio transparence is compromised.
C) The impedance ratio is very small (16 ohms to 4 ohms, compared to a few thousand ohms to 4 ohms). This simply means that it is much easier to achieve things like, frequency response extremes, than with a "typical" tube amp transformer. The ZEROs sport a frequence response of 2 Hz to 2 MHz.
